Quiz 16-Version Ww &. What is meant by the \"stable\" propagation of 1. How does
ID: 1864787 • Letter: Q
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Quiz 16-Version Ww &. What is meant by the "stable" propagation of 1. How does the fracture toughness of ceramkcs oompare with the fracture toughness of metals? A. Ke ls higher for ceramics than for metals B. K, i about the mme for onmies and met- A·The crack grows rapidly after reaching a crit- B. The erack grows slowly after reaching a crit- K, is lower for ceramics than for metals Ke is undefined for ceramics C. The crack grows slowly ao the stre" increases. D. The crack grows by ductile tearing. E. The crack does not grow at all E. It is impossible to generaliae 2. Why are ceramics sald to be defect-sensitive ma 7. What is meant by the "unstable propogation A. The erack grows rapidly after reaching a crit- A. No one will buy a defective ceramic B. Defects caase plastic failures in ceramics C Ceramics tend to fracture before yielding. D. Defects do not cause failure in ductile ma- ical size. B. The crck grows slowly after reaching a crit- C. The crack grows slowly as the stress incresses. D. The crack grows by ductile tearing E. The crack does not grow at all E. Vacancies cause fast fracture in ceramics 3. Why is it difficult to perform tensile tests on 8. Suppose small samples are eut from a large brittle materials? A. It is difficult to make brittle specimens the of a brittle material. Why is the average strength of the small samples greater than the strength of the original block? right size for tensile testing. Specimens tend to break where gripped by A. The ares Ag of a small sample is smaller, C. Machines measure oy only for ductile mate B. Flaws scale with sample size. C. The block contains more flaws per unit vol- D. Cutting tends to reduce or eliminate surface E.The block has a higher probability of con. machines are not powerful enough. E. Brittle samples break before yielding. 4, what is the modulus of rptu ure ?r fr a beam that fails in bending? taining a large flaw. A. Maximum sbear stress in the beam surface BMaximum tensile stress in the beam surface . Why do brittle materials often appear strongesr C. Maximum compressive stress D. Maximum tensile stress along the neutral in bending than in tension? A. It is difficult to make brittle specimens the right slze for tensile testing. B. Cracks twist out of their original orienta- E. Maximum shear stress along the neutral axis tion to propagate parallel to the compres C. The largest flaw may not be near the surface D. Bending tends to reduce or eliminate surface E. Tension causes maxcimum shear at 45 to 5. What is the fracture mechanism in a brittle of the material. solid in compression? A. Growth and linkage of cavities formed around B. Slow extension of many cracks to forma C. Rapid propagation of a single crack D. General plastic deformationExplanation / Answer
5.Rapid propagation of a single crack.
6.In stable crack propagation,the crack resist further extension unless applied stress is increased.
7. In unstable crack propagation, the crack increase rapidly after reaching critical size.
8. Cutting tends to reduce surface flaws.
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